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The development of fluorescent probe for hydrazine (N2H4) detection has attracted much attention due to the important role of N2H4 plays in the fields of medicine, agriculture, biology and environments. In this paper, the optical properties and water solubility of two novel two-photon fluorescent molecular probes (Probe1 and Probe2) before and after the reaction with N2H4 are studied by using the density function theory. The results show that electronic distribution and transition dipole moment of the probes are obviously changed after the reaction with N2H4, thus the optical properties of the molecules are influenced and the detection of N2H4 are realized. In addition, photoinduced electron transfer processes for Probe1 and Probe2 in the presence of N2H4 are theoretically characterized, which explains the experimental observations from the microscopic mechanism. Special attention has been paid on the analysis of the two-photon absorption for the probes with the absence and presence of N2H4 by the response theory method. Both probes with good water solubility show large variation on the two-photon absorption cross section when reacts with N2H4. In particular, the two-photon absorption response of Probe2 is more obvious, so it possesses preferable two-photon fluorescence microscopic imaging ability. More importantly, the receptor effect on the sensing performances of the probes are demonstrated, providing a theoretical reference for the design and synthesis on more efficient two-photon fluorescence N2H4 probes. Our study provides necessary information on the response mechanism of the studied chemosensors and helps to establish the relationship between the structure and optical properties of two-photon fluorescence N2H4 probes. [ABSTRACT FROM AUTHOR]

We present the first example of an 99 TcO 4 - anion entrapped within the cavity of a silver cluster, revealing an unprecedented photoinduced charge transfer phenomenon. [Ag 24 (C≡C t Bu) 20 ( 99 TcO 4 )]·(BF 4 ) 3 (denoted as 99 TcO 4 - @Ag 24 ) was successfully synthesized and structurally characterized. Single-crystal X-ray diffraction and Raman spectroscopy reveal that the tetrahedral structure of the 99 TcO 4 - anion sustains significant symmetry breaking with weakened Tc-O bond strength under confinement within the Ag 24 (C≡C t Bu) 20 4+ cluster. Notably, 99 TcO 4 - @Ag 24 exhibits a broadband electronic absorption spectrum in the visible region, which was absent for the other 99 TcO 4 - -containing compounds. Density functional theory calculations elucidate that host-guest electrostatic interactions result in an electron polarization effect between the 99 TcO 4 - anion core and the Ag 24 cationic shell. The emergence of an absorption band in 99 TcO 4 - @Ag 24 is rationalized by intermolecular charge transfer from the Ag 24 electronic states to the lowest unoccupied molecular orbitals of 99 TcO 4 - instead of the intramolecular electron transition observed in other 99 TcO 4 - -containing compounds.

To study the binding of rutin and serum albumin (SA) in physiological condition and the quenching mechanism of the fluorescence of SA by rutin, the fluorescence method was used. The results shows that the emission spectra of BSA (HSA) in the presence and absence of rutin are different. The emission spectra of BSA (HSA) in the presence of rutin can be quenched. The quenching mechanism of rutin to SA was static quenching with non-radiation energy transfer with single molecule. The binding constants K(A), the number of binding sites n and the thermodynamic parameters of the reaction of rutin with SA were determined at different temperatures. At 295 and 310 K, for BSA, K(A)(L * moL(-1)) = 4.215 x 10(4) and 6.996 x 10(3) and n = 0.75 and 0.64, respectively; for HSA, K(A)(L * moL (-1)) = 2.660 x 10(4) and 4.110 x 10(3) and n = 0.70 and 0.60, respectively. The binding constants K(A) decreased with the increase in temperature, which means that rutin and SA have a quite strong ability to form a new complex-system. The main binding force was discussed by thermodynamic equation, and the result is that deltaH < 0 and deltaS < 0 for the reaction of rutin with SA. So the binding forces was mainly H-bond and Van der Waals. The effect of the drug on the conformation of serum albumin was also studied by using synchronous fluorescence spectroscopy. Rutin could be deposited and transported by serum protein in vivo. Rutin had nearly no effect on the serum protein conformation.